The Soil Geochemical Atlas of Portugal: Overview and applications

The continental area of Portugal is now entirely covered by a soil geochemical survey (1 site/135 km²), taking as the sampling media topsoils (upper mineral horizons, A) and organic horizons (humus, O). Standard methods for sampling, sample preparation and analysis were used in order to achieve high quality and consistent data. Each sample was analyzed for 32 chemical elements, pH, electrical conductivity and organic matter content.The main purpose of the survey was to obtain baseline levels for various chemical elements. The compilation of all data (nearly 45,000 individual data) in an organised way, led to the production of the first Soil Geochemical Atlas of Portugal. In this Atlas it is possible to find for each chemical element a set of information statistics (basic statistical parameters, boxplots, cumulative frequency curves, etc.), maps of spatial distribution, among other information of geochemical and environmental interest. This paper gives an overview of the Soil Atlas and examples of application. The data were used to calculate reference values for 9 elements of environmental importance and to obtain empirical formulae allowing the estimation of elements in the coarse fraction of soils (< 2.00 mm) from known concentration in a finer fraction (< 0.18 mm).     

Geochemical mapping and databases in Finland

Regional geochemical maps in Finland have been produced from many different programmes. The scale of sampling, the material collected and the analytical methods used varied according to the aim of the study. The entire country was covered at a reconnaissance scale using glacial till, groundwater, surface water and organic stream sediments as sampling media. Glacial till was sampled throughout the country at a regional scale. Local scale mapping and detailed geochemical studies are carried out in selected areas. The main analytical methods have been ICP-AES and ICP-MS, but other methods were used when necessary. In assaying solid material, both total decomposition and strong acid (aqua regia) leaching were used. The results are stored in ALKEMIA, a database developed in the geochemistry department of the Geological Survey of Finland. The data are available as tabulated ASCII files and as digital image files on diskettes, or as various types of symbol and colour maps from desired areas or map sheets. Two examples of the application of geochemical mapping data in prospecting and in environmental research are presented. Indications of the presence of gold and multiple-sulphide ore deposits have been the most useful results obtained from a prospecting standpoint. On the environmental side, reconnaissance scale geochemical mapping data gave more reliable information on the base cation concentration than bedrock maps, making them particularly valuable in devising an acidification assessment model.     

Geochemical Atlas of the Slovak Republic at a scale of 1:1,000,000

The Geochemical Atlas of Slovak Republic (49,036 km²) at a scale of 1 : 1,000,000 was compiled during 1991–1995 together with maps of associated geochemical and ecological features at a scale of 1 :200,000. Investigations were aimed at the evaluation of concentrations and distributions of Al, As, Ba, Be, Ca, Ce, Co, Cd, Cs, Cr, Cu, Fe, Ga, Hg, K, La, Li, Mg, Mn, Mo, Na, Ni, P, Pb, Rb, Sb, Se, Sn, Sr, Th, U, V, W, Y, Zn, Zr in groundwater (16,359 samples), stream sediments (24,422 samples), rocks (3839 samples), soils (9892 samples from 4946 profiles; A and C horizons of each profile were sampled) and forest biomass (the foliage of the forest tree species from 3063 plots was sampled). In groundwater field measurements of temperature, pH, conductivity, dissolved O₂, acidity, alkalinity were done. The evaluation was oriented to the natural radioactivity of the Slovak territory as follows: rocks (K, U, Th, U_tot and dose rate, 15,573 reference spectrometric points), radon risk and water (U_nat, ²²⁶Ra, ²²²Rn; 5271 samples). The main objective of the Geochemical Atlas was to construct single-component maps showing concentrations of chemical elements, compounds and measured parameters in the researched media of Slovakia at a scale of 1 : 1,000.000 and to create interactive databases of chemical composition and/or measured parameters of groundwater, biomass, rocks, soils, stream sediments and natural radioactivity, for the entire territory of the Slovak Republic. The single-component maps are not constructed in the part ‘Rocks’, where all the main rocks types of Slovakia are presented in the ‘Map of lithogeochemical rock types of Slovakia at a scale of 1: 500,000’. The edition of six atlases has been planned. In 1997 the first three atlases will appear (Groundwater, Biomass, Natural Radioactivity). Publishing of last three atlases (Rocks, Soils, Stream Sediments) is planned for 1998. Since the analytical works on stream sediments were finished during 1997, it was not possible to present here the results of that part of the Geochemical Atlas.     

Geochemical and mineralogical properties of sulfide-bearing fine-grained sediments in Finland

 The geochemical and mineralogical characteristics of bulk samples and various size fractions of sulfide-bearing fine-grained sediments in the Petalax area, western Finland, were studied with ICP-AES (aqua regia digestion and "total" digestion) and X-ray diffraction. The sediments, which are dominated by particles <0.06 mm (clay and silt size), are composed of phyllosilicates (micas, kaolinite, chlorite, vermiculite), quartz, feldspars, amphiboles, organic matter, and secondary S minerals. The chemical analyses show that Na, Ca, and Sr are enriched in the silt and sand fractions, that Zr is enriched in the silt fraction, and that the concentrations of all other studied metals (Al, Ba, Co, Cr, Cu, Fe, K, La, Mg, Mn, Nb, Ni, Sc, Th, Ti, V, Y, and Zn) increase from the sand to the clay fraction. Sodium, Ca, and Sr occur largely in poorly dissolved feldspars, which explains the distribution of these metals in the sediments. The increase in the concentrations of most metals in the clay fraction is interpreted to be the result mainly of an increase in phyllosilicates in this size fraction. A geochemical comparison between the sulfide-bearing fine-grained sediments and glacial till shows that the former are enriched in several potentially toxic metals. It is therefore argued that the hydrological and ecological problems associated with the sulfide-bearing sediments are related not only to the production of acidity in oxidized layers, but also to mobilization and dispersion of toxic metals. Strategies to minimize damage of freshwater systems in areas covered with sulfide-bearing fine-grained sediments are suggested. Received: 20 February 1997 · Accepted: 25 August 1997     

The fifth edition of the Atlas of Finland —thematic and methodological guidelines

Finland has a most extraordinary experience in the field of thematic and expecially atlas cartography. The traditions of national atlases go almost 100 years back through five extensive editions (1899, 1910, 1920, 1960 and the fifth 1977–1991). Thematically these atlases have acted as thruthful mirrors of the rather dramatic changes Finland has lived through both from the point of environment (including political boundaries), economy, settlement and cultural features. Methodologically the series of Finnish atlases show many interesting aspects of development, in many respects important new approaches have been introduced and also the fifth edition has in international reviews been described as “innovative”. Finally one can stress the purposeful geographical emphasis in the content of these atlases; they are no mechanistic interpretations of e.g. statistical data. The presently-day work in the field of national atlases faces many new demands. Automation has enhanced the cartographic processing of data, there is a much extended information base concerning all the aspects of the modern societies which must be taken into account and there is also a number of new outlets for the ready product (printed and numerical). The greater scope and diversity must not, however, restrict the scientific unbiased editorial work of analyzing and synthetizing the data for cartographic expression; a clearcut geographical philosophy must be the guideline. In the future the thematic and atlas cartography must also be dealt increasingly in problem-oriented and international frames.     

Geochemical Atlas of Slovakia and examples of its applications to environmental problems

Results of comprehensive geochemical mapping and thematic studies of the Slovak territory (rocks, soils, stream sediments, groundwaters, biomass, and radioactivity) in the first half of the 1990s led to several new research programmes in Slovakia, within the frame of which new methodologies for geochemical data evaluation and map visualization were elaborated. This study describes the application and elaboration of data from the Geochemical Atlas of the Slovak Republic at national and regional levels. Based on the index of environmental risk (I_ER = ΣPEC/PNEC), the level of contamination for the geological component of the environment in Slovakia was evaluated. Approximately 10.5% of Slovakia’s territory was characterized as being environmentally disturbed to highly disturbed. In the areas where environmental loadings have accumulated, 14 regions where environmental risks existed due to high element concentrations were defined. The model calculations of health risk estimates based on the databases of the Geochemical Atlas for groundwater and soils indicate that the possible risk occurrence of carcinogenic diseases from groundwater arsenic contents is high in more than 10% of Slovakia, whereas the chronic risk is negligible. To determinate the background and threshold levels a combined statistical–geochemical approach was developed and applied as an example for groundwater at the national level as well as for single groundwater bodies. The results of statistical method application for the whole groundwater body (GBW) were compared with the background values for anthropogenically non-influenced areas in GBW. Final background value took into account time variations and spatial distribution of the element in GBW. Furthermore, based on the database from the Geochemical Atlas for groundwater, groundwater bodies potentially at qualitative risk were delineated for the whole of Slovakia. From a total of 101 groundwater bodies 17 were characterized as being at risk and 22 as being at possible risk.     

Geochemical and mineralogical aspects of sulfide mine tailings

Tailings generated during processing of sulfide ores represent a substantial risk to water resources. The oxidation of sulfide minerals within tailings deposits can generate low-quality water containing elevated concentrations of SO₄, Fe, and associated metal(loid)s. Acid generated during the oxidation of pyrite [FeS₂], pyrrhotite [Fe_(1−x)S] and other sulfide minerals is neutralized to varying degrees by the dissolution of carbonate, (oxy)hydroxide, and silicate minerals. The extent of acid neutralization and, therefore, pore-water pH is a principal control on the mobility of sulfide-oxidation products within tailings deposits. Metals including Fe(III), Cu, Zn, and Ni often occur at high concentrations and exhibit greater mobility at low pH characteristic of acid mine drainage (AMD). In contrast, (hydr)oxyanion-forming elements including As, Sb, Se, and Mo commonly exhibit greater mobility at circumneutral pH associated with neutral mine drainage (NMD). These differences in mobility largely result from the pH-dependence of mineral precipitation–dissolution and sorption–desorption reactions. Cemented layers of secondary (oxy)hydroxide and (hydroxy)sulfate minerals, referred to as hardpans, may promote attenuation of sulfide-mineral oxidation products within and below the oxidation zone. Hardpans may also limit oxygen ingress and pore-water migration within sulfide tailings deposits. Reduction–oxidation (redox) processes are another important control on metal(loid) mobility within sulfide tailings deposits. Reductive dissolution or transformation of secondary (oxy)hydroxide phases can enhance Fe, Mn, and As mobility within sulfide tailings. Production of H₂S via microbial sulfate reduction may promote attenuation of sulfide-oxidation products, including Fe, Zn, Ni, and Tl, via metal-sulfide precipitation. Understanding the dynamics of these interrelated geochemical and mineralogical processes is critical for anticipating and managing water quality associated with sulfide mine tailings.     

Geochemical aspects of some accumulation models for primary magmas

The compositions of primary magmas depend to some degree on the dynamic processes occurring in the partially molten region of the mantle. The compositional dependence is estimated for three models which assume either accumulation from a migmatized source region or accumulation entirely by the interstitial flow of magma. Accumulation from a migmatised region results in magmas with higher concentrations of incompatible elements than does batch melting, whereas accumulation by interstitial flow results in magmas with lower concentrations of these elements. The concentrations of refractory elements are almost independent of both the accumulation process and the degree of partial melting and are therefore usefull for the identification of primary magmas.     

Groundwater discharge to the Gulf of Finland (Baltic Sea): ecological aspects

The Gulf of Finland lies in the eastern part of the Baltic Sea. The surface area is 29,700 km² and the average depth of the basin is 38 m. Groundwater discharge to the Gulf of Finland equals 0.6 km³/year and this discharge is composed of many different chemical compounds. Groundwater discharge into the Gulf of Finland is dispersal. The coastal area of the Gulf of Finland can be divided into four zones with different geological, hydrogeological and discharge properties. The amount of direct groundwater discharge to the sea may be estimated using several geological and hydrogeological methods.     

Geochemical aspects of permeability controlled partial melting and fractional crystallization

Magma accumulation in the mantle requires that the mantle be permeable. Experimental investigations show that the permeability threshold first will be attained after a certain degree of partial melting. The influence of the permeability threshold on the composition of partial melts is evaluated using the fayalite-forsterite system as an example. In addition the variation in trace element concentrations are calculated for different distribution coefficients. Primary magmas formed by accumulation when a minimal degree of partial melting is required for permeability display a remarkably small variation in composition up to 30% partial melting. It is suggested from REE abundances that primary tholeiitic magmas have been generated by permeability controlled partial melting. The compositions of the primary magmas generated by permeability controlled partial melting will not differ much from the compositions obtained by batch melting, but the degrees of partial melting will differ for similar compositions.     

Origin of layered continental mantle (Karelian craton, Finland): Geochemical and Re–Os isotope constraints

Studies of mantle xenolith and xenocryst studies have indicated that the subcontinental lithospheric mantle (SCLM) at the Karelian Craton margin (Fennoscandian Shield) is stratified into at least three distinct layers cited A, B, and C. The origin and age of this layering has, however, remained unconstrained. In order to address this question, we have determined Re–Os isotope composition and a comprehensive set of major and trace elements, from xenoliths representing all these three layers. These are the first Re–Os data from the SCLM of the vast East European Craton.

Xenoliths derived from the middle layer B (at  110–180 km depth), which is the main source of harzburgitic garnets and peridotitic diamonds in these kimberlites, are characterised by unradiogenic Os isotopic composition. ¹⁸⁷Os/¹⁸⁸Os shows a good correlation with indices of partial melting implying an age of  3.3. Ga for melt extraction. This age corresponds with the oldest formation ages of the overlying crust, suggesting that layer B represents the unmodified SCLM stabilised during the Paleoarchean. Underlying layer C (at 180–250 km depths) is the main source of Ti-rich pyropes of megacrystic composition but is lacking harzburgitic pyropes. The osmium isotopic composition of layer C xenoliths is more radiogenic compared to layer B, yielding only Proterozoic T_RD ages. Layer C is interpreted to represent a melt metasomatised equivalent to layer B. This metasomatism most likely occurred at ca. 2.0 Ga when the present craton margin formed following continental break-up. Shallow layer A (at  60–110 km depth) has knife-sharp lower contact against layer B indicative of shear zone and episodic construction of SCLM. Layer A peridotites have “ultradepleted” arc mantle-type compositions, and have been metasomatised by radiogenic ¹⁸⁷Os/¹⁸⁸Os, presumably from slab-derived fluids. Since layer A is absent in the core of the craton, its origin can be related to Proterozoic processes at the craton margin. We interpret it to represent the lithosphere of a Proterozoic arc complex (subduction wedge mantle) that became underthrusted beneath the craton margin crust during continental collision  1.9 Ga ago.     

Geochemical studies on urban soil from two sampling depths in Tampere Central Region,Finland

Preliminary geochemical mapping was carried out within urban areas in Tampere Central Region, Finland, to gain a better understanding of element concentrations in urban soil and to provide information on baselines in soil within urban centres for soil contamination assessment purposes. The soil samples were taken from central city parks, day-care centres and school yards, and residential areas. Various sampling depths have generally been used in urban geochemical surveys. The aim of this study was to compare the results from two commonly used sample types taken from the same sites in urban soil: single samples of minerogenic topsoil from the 0–25 cm layer and composite samples of minerogenic topsoil from a depth of 0–2 cm. The concentrations of most of the studied trace elements showed a significant correlation between samples from 0 to 2 and 0 to 25 cm, but element concentrations differed between the two studied sample depths. For most of the studied elements, the median concentrations were higher in the 0–25 cm samples, but anomalous concentrations were more often found in the 0–2 cm samples. Some elements had elevated concentrations when compared with the Finnish guideline values for soil contamination assessment. This study did not conclusively establish whether a sampling depth of 0–2 or 0–25 cm should be recommended for similar studies in the future. Selection of the sampling depth in geochemical studies greatly depends on the aim of the project. In order to determine the upper limits of geochemical baseline variation, the deeper sampling depth appears to be more feasible. However, for the preliminary health risk assessment of areas with sensitive land uses, e.g. children’s playgrounds, samples from 0–2 cm depth are considered informative. Such samples may also be used to indicate local sources of dusting creating site-specific hotspots of potentially harmful elements in urban topsoil.     

地壳全元素探测——构建“化学地球”

地壳物质探测是地壳探测工程的重要组成部分。化学元素是地球物质组成的最基本单位,被称为地球的基因。矿产资源是由化学元素组成的,环境是受化学元素行为制约的,因此,对地壳中所有元素精确含量和分布的探测,对解决人类所面临的资源和环境问题具有重大意义。地壳全元素探测项目拟发展4种地球化学探测技术,包括地壳中所有天然元素的精确分析技术,中下地壳物质成分识别技术,穿透性地球化学探测技术,海量地球化学数据和图形显示技术。建立1个覆盖全国的地球化学基准网,系统采集代表性岩石样品10000件,疏松物样品6000件,按标准化的方法分析其主量元素和微量元素含量(包含78种元素),建立中国大陆地球化学基准值,为研究化学元素的分布、演化和成矿物质背景提供基准参考数据。进行总长度3300km的3条地球化学走廊带的实验与示范,采集各类代表性岩石样品5000件,进行元素和同位素测定,构建走廊带地壳地球化学模型、跨越不同大地构造单元的元素空间变化和大型矿集区成矿物质背景。为开展全国地壳探测工程奠定基础,并为最终建立化学地球进行技术准备和先导性实验。     

Structural aspects of the Middle and the High Atlas (Morocco) phenomena and causalities

Since the beginning of the Mesozoic the structural development of the Middle Atlas and the central High Atlas was controlled by a pre-existent fault pattern, which was reactivated repeatedly in various manners.The fault pattern is characterized by two main directions. The first runs 35–45° and dominates in the Middle Atlas, the second runs 70° and is common in the southern part of the central High Atlas; between these regions both directions overlap. In the Atlas of Demnat, Beni Mellal and El Ksiba at the northern border of the central High Atlas a further direction, the one of 120°, locally gains in significance. Into the gores of the pattern commonly magmatites intruded during the Mesozoic, in the course of the following compressive deformation often a cleavage was formed there.The compressive deformation started in the Oligocene; the directon of the main compressional stress ₁ lay at 160°. Dependant on their orientation to ₁ the pre-existent faults reacted differently on this stress: The 70° faults were reactivated as upthrusts, the 35° ones as sinistral oblique slip reverse faults and those of 120° as dextral oblique slip reverse faults. At the northwestern border of the hinge area between the Middle and the High Atlas this scheme of movements was complicated by an interference with movements along the Transalboran fault system.Because of changes in the style of deformation the so-called B-B fault zone, running ENE from El Ksiba to Aghbala, can be defined as the structural border between the High and the Middle Atlas.

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Zusammenfassung Die strukturelle Entwicklung des Mittleren Atlas und des zentralen Hohen Atlas seit dem Beginn des Mesozoikums wurde durch ein Bruchmuster präexistenter Störungen gesteuert, die sich im Verlauf dieser Zeit wiederholt in verschiedener Weise durchgepaust haben.Das erwähnte Bruchmuster wird durch zwei Hauptrichtungen charakterisiert, deren eine von 35–45° im Mittleren Atlas vorherrscht, während die andere von 70° für den südlichen Teil des zentralen Hohen Atlas bestimmend ist, in einem Zwischenbereich überlappen sich beide Richtungen. Im Atlas von Demnat, Beni Mellal und El Ksiba am Nordrand des Hohen Atlas tritt lokal begrenzt eine weitere Richtung von 120° hinzu. In die Zwikkel des Bruchmusters drangen im Verlauf des Mesozoikums verbreitet Intrusiva ein, während der anschließenden kompressiven Deformation wurde dort häufig eine Schieferung angelegt.Die kompressive Deformation setzte im Oligozän ein, wobei die Richtung der kompressiven Hauptnormalspannung ₁ ca. 160° betrug. Die präexistenten Störungen reagierten auf dieses Stressfeld je nach ihrer Lage zu ₁ unterschiedlich: Die 70°-Störungen wurden als Aufschiebungen reaktiviert, die 35°-Störungen als sinistrale Schrägaufschiebungen und die 120°-Störungen als dextrale Schrägaufschiebungen. Kompliziert wurde dieses Bewegungsschema am Nordwestrand des Scharnierbereiches zwischen Hohem und Mittlerem Atlas durch eine Überlagerung mit Bewegungen entlang des Transalboran-Störungssystems.Als strukturelle Grenze zwischen Hohem und Mittlerem Atlas kann aufgrund von Änderungen im Baustil die sog. B-B-Störungszone, die von El Ksiba Richtung nach ESE bis Aghbala verläuft, angesehen werden.

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Résumé Depuis le début du Mésozoïque, l'histoire structurale du Moyen-Atlas et du Haut Atlas central aété déterminée par un réseau de failles préexistantes qui ont été réactivées à diverses reprises et de diverses manières.Ce réseau de failles est caractérisé par deux directions principales: l'une (35° à 45°) domine dans le Moyen Atlas, l'autre (70°) dans la partie sud du Haut Atlas central. Entre ces deux régions, les deux directions coexistent. Dans l'Atlas de Demnat, de Beni Mellal et d'El Ksiba, à la bordure nord du Haut Atlas central, une troisième direction (120°) présente une importance locale. Pendant le Mésozoïque, des magmas se sont intrudés dans les ouvertures du réseau, tandis qu'une schistosité apparaissait souvent dans les régions en compression.La déformation compressive a débuté à l'Oligocène, avec une contrainte principale ₁ orientée à 160°. Les failles préexistantes ont réagi de manières différentes, selon leur orientation par rapport à ₁: les failles de direction 70° ont été réactivées en chevauchement, les failles à 35° ont donné des failles inverses à jeu oblique sénestre, et les failles à 120° des failles inverses à jeu oblique dextre. Le long de la bordure nord-ouest de la zone charnière entre le Moyen et le Haut Atlas, ce schéma s'est compliqué par interférence avec des mouvements le long de l'accident transalborien.Eu égard aux changements dans le style de la déformation, la zone failleuse dite B-B, qui s'étend en direction ENE de El Ksiba à Aghbala, peut se définir comme la frontière structurale entre le Haut et le Moyen Atlas.

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, . : 35–45° , 70° ; . Demnat, Beni Mellal El Ksiba 120°. , . , , , I₁ 160°. , I₁: 70° , 30° , 120° - . - Transalboran. .. -, E-S Aghbala.

     

Geochemical exploration of a Precambrian Batholith, source of a Cu-W mineralization of the tourmaline breccia in Southern Finland

The Hämeenkyrö batholith is a round-shaped plutonic body of an areal size of 147 km². It is composed of calc-alkaline to alkaline rocks that intruded previously metamorphosed Svecofennian volcanogenic and sedimentary schists 1860 Ma ago. The Cu-W bearing tourmaline breccia of the Ylörvi deposit occurs in metavolcanic rocks close to the eastern contact of the batholith.The average sampling density in the batholith was 1 sample per km², and 175 samples were analyzed for Cu, Au, Ag, Ni, Pb, Co, Zn, S by AAS for SiO₂, TiO₂, Al₂O₃, FeO, MnO, MgO, CaO, Na₂O, K₂O, As, Sn and P by X-ray fluorescence. Mo and W were determined colorimetrically. Barth mesonorms were calculated for each sample and the rock type was determined according to Streckeisen's classification. Element distributions are displayed on contour maps.The rock types of the batholith exhibit an asymmetric concentric arrangement, the order from the center towards the margin being alkali-feldspar granite, syenogranite, monzogranite, quartz monzonite, quartz syenite, alkali-feldspar, quartz syenite, syenite and alkali-feldspar syenite. Anomalously high Cu, As, Sn, S, K₂O and Na₂O contents have been found at the eastern margin of the batholith in a N—S-trending zone, which is characterized by hydrothermal alteration phenomena, propylitization, tourmalinization and scapolitization. Three anomalous areas have been defined within this zone, one of them is associated with the Ylöjärvi deposit and the other two are regarded as exploration targets.     

Geochemical Baselines of Nickel and Chromium in Various Surficial Materials in the Barents Region, NW Russia and Finland

The geochemical baselines of nickel and chromium were studied from the data produced by the Barents Ecogeochemistry project, a large international regional geochemical mapping exercise. The project surveyed major and trace element distributions in stream water, organic and mineralogically-modified soil horizons, and terrestrial moss in the northwestern part of Russia and in Finland. Other materials were collected during the pilot phase and later from thirty special sites. The results on respective materials by XRF, ICP-MS and ICP-AES showed that both geological and anthropogenic factors have an influence on the geochemical baseline concentrations of Ni and Cr in organic soil and stream water. The main explanation of the observed distribution patterns in terrestrial moss is human activity, but geological factors can also affect the baselines. The variation of geochemical baselines in the mineral-rich soil horizon depends only on variations in bedrock. The mineralogy of samples mainly controls the leachability properties of soil samples.     

Geochemical and thermodynamic aspects of sorption of strontium on kaolinite dominated clay samples at Kalpakkam

The mobility of strontium in subsurface is largely influenced by sorption on to clay minerals. In the present study, kaolinite clay samples collected from the Kalpakkam nuclear plant site were employed to understand the sorption characteristics of strontium by batch method. The effect of several parameters such as time, strontium ion concentration, pH, temperature and ionic strength was investigated. The kinetic studies suggested pseudo-second-order mechanism. The experimental sorption data was fitted to Langmuir adsorption model for obtaining the sorption capacity of the sorbent. The maximum sorption capacity was 5.77 mg/g at 298 K and was found to increase with an increase in temperature. It was observed that the distribution coefficient (K _d) of strontium on clay increased as the pH of the solution increased. The distribution coefficient was found to decrease with an increase in concentration of Na⁺ and Ca²⁺ ions. This variation of K _d suggests that cation exchange is the predominant sorption process. It was also observed that sorption process is endothermic. The thermodynamic parameters such as ∆G ⁰, ∆H ⁰ and ∆S ⁰ were calculated. The negative values obtained for ∆G ⁰ indicated that the sorption of strontium on clay was spontaneous at all studied concentrations. ∆G ⁰ becomes more negative with an increase in temperature, suggests that the sorption process is more favorable at higher temperatures.